src/nmutil/sim_tmp_alternative.py

   1 """Run-time selection of simulator engine
   2
   3 Usage::
   4
   5     from nmutil.sim_tmp_alternative import Simulator
   6
   7 Then, use :py:class:`Simulator` as usual.
   8
   9 This should be backwards compatible to old developer versions of nMigen.
  10
  11 To use cxxsim, export ``NMIGEN_SIM_MODE=cxxsim`` from the shell.
  12 Be sure to check out the ``cxxsim`` branch of nMigen, and update yosys
  13 to the latest commit as well.
  14
  15 To use pysim, just keep ``NMIGEN_SIM_MODE`` unset.
  16 Alternatively, export ``NMIGEN_SIM_MODE=pysim``.
  17
  18 Example::
  19
  20     $ export NMIGEN_SIM_MODE=...  # pysim or cxxsim, default is pysim
  21     $ python ...
  22
  23 or, even::
  24
  25     $ NMIGEN_SIM_MODE=...  python ...
  26 """
  27
  28 import os
  29
  30 try:
  31     from nmigen.sim import Simulator as RealSimulator
  32     detected_new_api = True
  33 except ImportError:
  34     detected_new_api = False
  35     try:
  36         from nmigen.sim.pysim import Simulator as RealSimulator
  37     except ImportError:
  38         from nmigen.back.pysim import Simulator as RealSimulator
  39
  40 nmigen_sim_environ_variable = os.environ.get("NMIGEN_SIM_MODE") \
  41                               or "pysim"
  42 """Detected run-time engine from environment"""
  43
  44
  45 def Simulator(*args, **kwargs):
  46     """Wrapper that allows run-time selection of simulator engine"""
  47     if detected_new_api:
  48         kwargs['engine'] = nmigen_sim_environ_variable
  49     return RealSimulator(*args, **kwargs)
  50
  51
  52 def is_engine_cxxsim():
  53     """Returns ``True`` if the selected engine is cxxsim"""
  54     return nmigen_sim_environ_variable == "cxxsim"
  55
  56
  57 def is_engine_pysim():
  58     """Returns ``True`` if the selected engine is pysim"""
  59     return nmigen_sim_environ_variable == "pysim"
  60
  61
  62 nmigen_sim_top_module = "top." if is_engine_pysim() else ""
  63 """Work-around for cxxsim not defining the top-level module"""